Abstract
To stimulate muscle protein synthesis, it is important to increase the plasma levels of essential amino acids (EAA), especially leucine, by ingesting proteins. Protein hydrolysate ingestion can induce postprandial hyperaminoacidemia; however, it is unclear whether protein hydrolysate is associated with higher levels of aminoacidemia compared with a free amino acid mixture when both are ingested orally. We assessed the effects of whey protein hydrolysate (WPH) ingestion on postprandial aminoacidemia, especially plasma leucine levels, compared to ingestion of a free amino acid mixture. This study was an open-label, randomized, 4 × 4 Latin square design. After 12–15 h of fasting, 11 healthy young men ingested the WPH (3.3, 5.0, or 7.5 g of protein) or the EAA mixture (2.5 g). Blood samples were collected before ingestion and at time points from 10 to 120 min after ingestion, and amino acids, insulin, glucose and insulin-like growth factor-1 (IGF-1) concentrations in plasma were measured. Even though the EAA mixture and 5.0 g of the WPH contained similar amounts of EAA and leucine, the WPH was associated with significantly higher plasma EAA and leucine levels. These results suggest that the WPH can induce a higher level of aminoacidemia compared with a free amino acid mixture when both are ingested orally.
Highlights
Muscle mass can be considered one of the most important components of the human body because it generates force and movement and is a major site of metabolism
We previously demonstrated that the ingestion of whey protein hydrolysate (WPH) was associated with a greater increase in muscle protein synthesis (MPS) compared with an amino acid mixture in rodents [15]
There were no significant differences between the ingestion of the essential amino acids (EAA) mixture and of 3.3 g of the WPH in the plasma EAA concentration changes and area under the curves (AUCs)
Summary
Muscle mass can be considered one of the most important components of the human body because it generates force and movement and is a major site of metabolism. The amount of muscle mass is regulated by the net balance between muscle protein synthesis (MPS) and breakdown [1,2]. Ingestion of protein or amino acids can increase the net muscle protein balance, primarily because of the increase in MPS, with a lesser contribution from the decrease in muscle protein breakdown [3,4]. A rapid acute rise in postprandial circulating EAA or leucine levels following consumption of protein-rich food has been associated with increases in MPS [7,8,9]. Our previous rodent study demonstrated that hyperaminoacidemia following consumption of acidified milk was associated with a greater increase in MPS compared with skim milk, the milk drinks had the same types and quantities of protein [7]. Koopman et al [9] suggested that ingestion of casein
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